Heavy oil, a variety of petroleum, is an abundant energy source that is found throughout the world. Of the world's total oil reserves, an estimated 53 percent are in the form of heavy oil or bitumen (terms are used interchangeably). In fact, heavy oil production is estimated to increase by 200 percent by 2030. Like the so-called “bottom of the barrel” of conventional petroleum, heavy oil is typically carbon-rich and extremely dense. Heavy oil is also highly viscous, solid or near-solid at room temperature, and has low hydrogen content and a high mass density (e.g., API gravity of 20 degrees or less).
Despite its abundance, the refining of heavy oil has proven to be a challenge. Conventionally, multiple technologies are used to upgrade various forms of heavy fuel, as it has been difficult to accomplish the upgrading using a single technology. For example, “vacuum distillation bottoms,” which is liquid at 300-400° C. but remains a solid at room temperature, represents one of the most difficult types of heavy oil in a refinery to handle and transport. However, as the value of regular crude oil continues to increase, the need to upgrade heavy oil to a synthetic crude oil will continue to increase.
Circulating fluidized bed boilers can burn refinery by-products efficiently and cleanly. However, these fuels tend to be difficult to handle because they exit the refinery in liquid form at elevated temperatures and must be directly introduced into a combustor in this form. Circulating fluidized bed combustion (CFB) is a conventional industrial process normally used for coal and petcoke combustion, and has been the basis for the development of chemical looping combustion processes.
Chemical looping combustion (CLC) is a specific type of combustion process that was originally created in the 1950s to produce CO2, but recently it has received increased attention as a potential CO2 capturing process. In a conventional CLC process, an oxygen transfer material or “oxygen carrier” acts as an intermediate transporter of oxygen between two different reaction zones. The first zone where the fuel is injected is called a fuel reactor, and the second zone is called an air reactor, as air is injected into it to oxidize the oxygen carrier. Therefore, the CLC process prevents the direct contact of the air and the fuel. Typically, a solid metal oxide oxygen carrier is used to oxidize the fuel stream in a fuel reactor. This results in the production of CO2 and H2O. The reduced form of the oxygen carrier is then transferred to the air reactor, where it is contacted with air, re-oxidized to its initial state, and then returned back to the fuel reactor for further combustion reactions. CLC processes using a liquid hydrocarbon feed are known in the art. However, these processes do not upgrade heavy oil feeds into higher-value petroleum-based products in a single process.
Thus, there is a need for a single technology for upgrading heavy fuel to produce valuable petroleum-based products for use in power generation.